Pneumatic amplifiers

ABSTRACT

There is described a pneumatic amplifier comprising a housing, a diaphragm dividing the housing into first and second chambers, an inlet port to the first chamber for receiving an input signal, an exhaust port from the second chamber, a manifold in the second chamber, an inlet port to the manifold for a supply of pressure air, and an outlet from the manifold for an amplified output signal, the manifold having at least one axially offset orifice confronting the diaphragm. The amplified output signal is used to control the position of a movable member, for example a valve member. A feed-back connection may be provided between the movable member and the amplifier and a setting device may control the input signal.

United States Patent [191 [451 Feb. 26, 1974 Riley y [54] PNEUMATICAMPLIFIERS [76] Inventor: John Terence Riley, Bank St.,

Walshaw, Bury, England [22] Filed: Feb. 9, 1972 [2]] Appl. No.: 224,838

[30] Foreign Application Priority Data Feb. ll, 1971 Great'Britain4439/71 Feb. ll, 1971 Great Britain 4440/7l [52] US. Cl. 137/82, 251/28[51] lnt. Cl. G05d 16/06 [58] Field ofSearch ..137/82, 625.33, 625.61,as. 7/625.6 6; 251/367 [56] References Cited I UNITED STATES PATENTS765,925 7/1904 lbach et al. l37/625.33 X

FOREIGN PATENTS OR APPLICATIONS 1,027,402 4/1966 Great Britain 137/82Primary ExaminerArnold Rosenthal Attorney, Agent, or FirmBrovvne,Beveridge, De- Grandi & Kline 5 7 ABSTRACT There is described apneumatic amplifier comprising a housing, a diaphragm dividing thehousing into first and second chambers, an inlet port to the firstchamber for receiving an input signal, an exhaust port from the secondchamber, a manifold in the second chamber, an inlet port to the manifoldfor a supply of pressure air, and an outlet from the manifold for anamplifled output signal, the manifold having at least one axially offsetorifice confronting the diaphragm. The amplified output signal is usedto control the position of a movable member, for example a valve member.A feed-back connection may be provided between the movable member andthe amplifier and a setting device may control the input signal.

9 Claims, 7 Drawing Figures PATENTEDFEBZBIQM 3,794,058

sum 1 OF 2 ah I 1 I 15 I I-5.1 19 20 1e 17 DIAPHRAGM AREA (11;) 73 14 K7/7 41 15 7O PNEUMATIC AMPLIFIERS Thisinvention relates to pneumaticamplifiers and to apparatus incorporating pneumatic amplifiers forcontrolling the position of movable members.

'According to the invention a pneumatic amplifier comprises a housing, adiaphragm dividing the housing into first and second chambers, an inletport to the first chamber for receiving an input signal, an exhaust portfrom the second chamber, a manifold in the second chamber, an inlet portto the manifold for a supply of pressure air, and an outlet from themanifold for an amplified output signal, the manifold having at leastone axially offset orifice confronting the diaphragm.

The amplifier output signal may be used to control the position of amovable member, for example a valve member, and there may be a feedbackconnection between the movable member and the amplifier; for example thefeedback connection may be a spring acting between the movable memberand the diaphragm.

There may be a manually adjustable setting device to control the inputsignal to the amplifier so that for example if the valve controls themovement of a machine tool slide, the slide speed may be adjusted byadjusting the setting device.

- The invention may be performed in various ways and some specificembodiments will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 is a schematic section through a pneumatic amplifier;

FIG. 2 is an end view of FIG. 1;

FIG. 3 is an elevation, part in axial section, of an arrangement forcontrolling a valve;

FIG. 4 is similar to FIG. 3 but shows a' modified arrangement;

FIG. 5 is an elevation of a web sensing device;

FIG. 6 is a section on the line VlVl of FIG. 5; and

FIG. 7 shows part of another arrangement.

Referring generally to the drawings, in control systems it is oftennecessary to control a movable member, such as the valve member of avalve, in response to low pressure air signals (approx. 4 inches H O).Normally, in order to obtain enough force to operate the valve, a largediaphragm is used to respond to the air signal and produce a force whichacts on the valve, this has the disadvantage of giving a slow responseto input signal variations.

With the'present arrangements, by amplifying the air signal beforeapplying it to the valve, the same force can be obtained with a muchsmaller diaphragm.

The arrangements are basically a proportional pneumatic amplifier in twoforms, either with or without feedback.

Referring to FIGS. 1 and 2, a pneumatic amplifier 10 comprises a housing11, a diaphragm 12 extending across the housing and peripheralllysecured to a wall 13 of the housing to divide the housing into chambers14 and 15. The diaphragm comprises a rigid flat circular central portionconnected to a flexible annular portion 17 itself connected to wall 13and of outer effective diameter D,. An input air signal may enter thechamber 14 at 18. Chamber is connected to exhaust at 19. A manifold 20is disposed in chamber 15 and is connected at 21 to a source of airunder pressure through a restrictor 22 and has an aperture at 23 for anoutput signal.

A flat wall 24 of the manifold opposite the diaphragm portion 16 hasthree orifices f,, f f through which air under pressure constantlyescapes to impinge on the diaphragm. The orifices are equally angularlyspaced on a circle of diameter D (FIG. 2) and are of equal diameter DThe low pressure input signal at 18 causes the diaphragm to move closerto orifices f f )2, until the pressure built up in the manifold producesa force over the areas of the orifices to balance the force on thediaphragm due to the input signal.

At balance:

P 141 3P2A2 (S68 Three orifices are used, instead of a single centralone, to increase the diameter over which the balancing force acts. Thisincrease in diameter causes the diaphragm to sit squarely at rightangles to the axes of the orifices (the diaphragm does not actuallytouch the orifices) hence producing good consistency of amplification.If a single central orifice of three times the area were used thediaphragm would not always be positioned squarely, and would tend toengage the orifice, hence giving an inferior and inconsistentperformance.

The output signal of the amplifier is proportional to the input signal.

The diaphragm remains clear of the orifices and manifold throughout theworking range of the amplifier.

The air pressure delivered by the source to the manifold may be 5 psi.for example.

In an alternative arrangement the manifold has only one axially offsetorifice, e.g.,f,, the orifices f f being replaced by closed projectionsextending from the main plane of the manifold wall 24 the same distanceas the mouth of orifice f,. In this case the diaphragm will engage theclosed projections, and become slightly tilted, throughout the workingrange of the amplifier. However the output signal remains proportionalto the input signal, although the amplification formula given above doesnot apply.

There could be more than three offset orifices with or without closedprojections.

Referring now to FIG. 3, the amplifier is arranged to control themovement of a spool 31 in a proportional valve 30, that is the valve isprogressively opened or closed by movement of the spool. The spool 31 isbiassed in one sense by a spring 32 and in the other sense by airpressure in chamber 33 engaging a piston 34 in housing 35, the pistonbeing connected to the spool. The amplifier has an annular dust cover 36and an end wall 37 of the manifold engages an annular O-ring and a screw38 engages in a threaded central bore 39 in a wall of the amplifierhousing to mount the manifold. Air is supplied through an adaptor plug40 which incorporates a restrictor. The output signal acts on the piston34. The position of the valve spool may control the flow of oil to amachine tool slide so that the speed of the slide may be controlled bythe position of the spool.

In the arrangement of FIG. 4, unlike that of FIG. 3, a feedbackconnection is provided. The output signal in line 50 acts on piston 51connected to the spool of Amplification valve 52 and causing the spoolto move against the action of a strong helical spring 53 which at oneend abuts the valve spool are not shown.

The proportional fluid valve which the amplifier controls can be eitherpneumatic or hydraulic.

In FIG. 4 the feedback gives higher spool positioning accuracy,overcoming or reducing the effect of spool friction and forces due tofluid flow.

FIGS. 5 and 6 show an arrangement for sensing the position of the edgeof a web.

The sensor comprises an emitter nozzle 70 and a receiver nozzle 71 heldin accurate alignment by a body 72. The nozzles 70 and 71 may beslidable in the body 72 so as to be axially adjustable, or they may bethreaded therein.

An emitter input port 73 is supplied from a source with air underpressure and produces a jet of air between the nozzles 70 and 71. Theoutput port 74 of the receiver nozzle 71 is connected to the inlet portof the analogue pneumatic amplifier 10.

The diaphragm produces a force in relation to the position of a webbetween the nozzles and hence the pressure received at the inlet ofnozzle 71.

The pressure received at the inlet of the nozzle 71 is an analogue ofthe position of the edge 75 of the web 76.

The nozzles 70, 71 are in the form of slits, preferably but notnecessarily of the same dimensions, are preferably coplanar but could beat an angle to one another to vary the relationship between the pressurereceived at nozzle 71 with the length of nozzles 70 and 71. Thus thenozzles could be of equal length with the receiver nozzle slightly widerthan the other nozzle.

The output signal at 74 is arranged to be the input signal for thepneumatic amplifier.

When the edge of the web or sheet is at the desired central position asshown in FIG. 5, the output signal at 74 has a value ascertained bytesting. In use, if the web position deviates from central, the outputpressure at the outlet of the amplifier will change also in accordancevwith the characteristics of the system and this change can be used tooperate mechanism, such as a free piston, to move the web edge back tothe central position if required. If the web moves to the left in FIG. 5the output pressure increases, and if the web moves to the right, theoutput pressure decreases.

FIG. 7 shows part of an arrangement for selecting several presetsignals. This system is basically intended for speed control on machinetools where more than one adjustable speed is required for a particularmachine slide. An example is on capstan lathes where a speed is selectedfor each station of the turret. In this case the valve would be avariable restrictor.

Setting screws 80 are fitted to a disc 81 which is rotatable about anaxis 82 to select a number of predetermined settings by positioning theappropriate screw in line with cam 83.

Air from a suitable source (e.g., 5 psi) is supplied through hose 84 tooutlet nozzle 85 having a circular orifice opposed to a circular orificein aligned receiving nozzle 86.

The low pressure sensor output signal at 87 (approx. 10 inches watermax) is fed into an amplifier as described above, this signal causing anamplified signal to appear at port 23.

The speed setting screws contact the suitably shaped cam member 83,depressing the member against the action of a spring 89 connected to afixed part 90. A moving member 91 is pivoted at axis 94 and carries theair nozzle 85.

When the speed control screw 80 is screwed fully upwards in the Figure,to the position shown, the air nozzle is in line with the receivernozzle 86 and a maximum output pressure is obtained at the receivernozzle port 87.

If the speed screw is screwed in towards the member 83, the movingmember 91 is pivoted and the nozzles gradually move out ofline, thusproducing a falling output pressure. Over almost all the range ofadjustment the relationship between screw position and output pressureis linear so that the output signal is an analogue of the position ofthe screw.

I claim:

1. A pneumatic amplifier comprising a housing, a diaphragm having anaxis and dividing the housing into first and second chambers, an inletport to the first chamber for receiving an input signal, an exhaust portfrom the second chamber, a manifold in the second chamber having a wallconfronting said diaphragm, an inlet port to the manifold for a supplyof pressure air, and an outlet from the manifold for an amplified outputsignal, the manifold having a plurality of spaced axially offsetorifices confronting the diaphragm.

2. A pneumatic amplifier as claimed in claim 1, comprising at leastthree orifices equally angularly spaced around the axis of the diaphragmand equally spaced therefrom.

3. A pneumatic amplifier as claimed in claim 1 comprising three orificesof equal area equally angularly spaced around the axis of the amplifierand equally spaced therefrom.

4. A pneumatic amplifier as claimed in claim 2, in which each orifice iscircular and the centres of the orifices lie on a common circle.

5. A pneumatic amplifier as defined in claim 1 wherein said manifold hasthree spaced, axially offset, orifices of equal area confronting saiddiaphragm.

6. A pneumatic amplifier as defined in claim 1 wherein said manifold hasthree spaced, axially offset, circular orifices contronting saiddiaphragm.

7. A pneumatic amplifier as defined in claim 1 wherein said orifices aredefined by projections of substantially equal length extending from saidmanifold wall toward said diaphragm.

8. A pneumatic amplifier comprising a housing, a diaphragm having anaxis and dividing the housing into first and second chambers, an inletport leading into said first chamber for receiving an input signal, anexhaust port leading from said second chamber, a manifold in said secondchamber having a wall confronting said diaphragm, an inlet port leadinginto said manifold for providing a supply of pressure air, and an outletfrom said manifold for an amplified output signal, said manifold havingat least three orifices confronting said diaphragm, at least two of saidorifices being axially offmanifold to admit a supply of pressure air,and an outlet port from said manifold for an amplified output signal,said manifold having at least three projections extending substantiallyequal distances from said wall toward said diaphragm, at least one ofsaid projections defining an orifice offset from said diaphragm axis, atleast three of said projections including said at least one projectionbeing located on a common circle.

1. A pneumatic amplifier comprising a housing, a diaphragm having anaxis and dividing the housing into first and second chambers, an inletport to the first chamber for receiving an input signal, an exhaust portfrom the second chamber, a manifold in the second chamber having a wallconfronting said diaphragm, an inlet port to the manifold for a supplyof pressure air, and an outlet from the manifold for an amplified outputsignal, the manifold having a plurality of spaced axially offsetorifices confronting the diaphragm.
 2. A pneumatic amplifier as claimedin claim 1, comprising at least three orifices equally angularly spacedaround the axis of the diaphragm and equally spaced therefrom.
 3. Apneumatic amplifier as claimed in claim 1 comprising three orifices ofequal area equally angularly spaced around the axis of the amplifier andequally spaced therefrom.
 4. A pneumatic amplifier as claimed in claim2, in which each orifice is circular and the centres of the orifices lieon a common circle.
 5. A pneumatic amplifier as defined in claim 1wherein said manifold has three spaced, axially offset, orifices ofequal area confronting said diaphragm.
 6. A pneumatic amplifier asdefined in claim 1 wherein said manifold has three spaced, axiallyoffset, circular orifices contronting said diaphragm.
 7. A pneumaticamplifier as defined in claim 1 wherein said orifices are defined byprojections of substantially equal length extending from said manifoldwall toward said diaphragm.
 8. A pneumatic amplifier comprising ahousing, a diaphragm having an axis and dividing the housing into firstand second chambers, an inlet port leading into said first chamber forreceiving an input signal, an exhaust port leading from said secondchamber, a manifold in said second chamber having a wall confrontingsaid diaphragm, an inlet port leading into said manifold for providing asupply of pressure air, and an outlet from said manifold for anamplified output signal, said manifold having at least three orificesconfronting said diaphragm, at least two of said orifices being axiallyoffset with respect to said diaphragm and three of said orifices beinglocated on a common circle.
 9. A pneumatic amplifier comprising ahousing, a diaphragm having an axis and dividing said housing into firstand second chambers, an inlet port leading into said first chamber forreceiving an input signal, an exhaust port leading from said secondchamber, a manifold in said second chamber and having a wall confrontingsaid diaphragm, an inlet port leading into said manifold to admit asupply of pressure air, and an outlet port from said manifold for anamplified output signal, said manifold having at least three projectionsextending substantially equal distances from said wall toward saiddiaphragm, at least one of said projections defining an orifice offsetfrom said diaphragm axis, at least three of said projections includingsaid at least one projection being located on a common circle.